1. Field of the Invention
The present invention relates to image processing apparatuses, image processing methods, and programs. More specifically, the present invention relates to an image processing apparatus, an image processing method, and a program which perform processing for displaying a stereoscopic image, i.e., a three-dimensional (3D) image.
2. Description of the Related Art
In recent years, image capture apparatuses (cameras) for photographing images with multiple viewpoints have been developed which allow a stereoscopic image (a 3D image) to be displayed. Such an image capture apparatus photographs images with different viewpoints, for example, an image for the left eye and an image for the right eye.
For display of a three-dimensional image, an image for the left eye and an image for the right eye are displayed on a display section. A viewer wears liquid-crystal shutter glasses, polarized glasses, or the like to view the left-eye image and the right-image image with his or her left eye and right eye, respectively, so that he or she can view a three-dimensional image giving a stereoscopic effect. There are various three-dimensional-image display systems, such as a parallax barrier system that does use glasses, in addition to the aforementioned liquid-crystal shutter system and the polarized system.
In any of the systems, the viewer can get a sense of three dimensionality by individually viewing two images having a parallax with his or her left and right eyes. However, the position of an image seen by the viewer varies depending on the size of a display section on which two images photographed from different viewpoints are displayed.
This phenomenon will now be described with reference to FIGS. 1A to 1D. FIGS. 1A to 1C show, when the same pair of images (i.e., the same pair of an image for the left eye and an image for the right eye) is displayed on three different sizes of the display section (display), stereoscopic-image positions at which stereoscopic images of an object included in the display images are perceived.
FIGS. 1A, 1B, and 1C illustrate cases of a large-size display, a medium-size display, and a small-size display, respectively.
An example for the large-size display illustrated in FIG. 1A will be described first. As shown, the position of a stereoscopic image perceived by the viewer lies at the intersection of a line that connects the display position of the left-eye image on the display and the viewer's left eye and a line that connects the display position of the right-eye image on the display and the viewer's right eye. This is also true for the cases shown in FIGS. 1B and 1C.
As can be understood from FIGS. 1A to 1C, the larger the display size is, the larger the distance between the display position of the left-eye image on the display and the display position of the right-eye image on the display (i.e., the parallax on the display) becomes. Conversely, the smaller the display size is, the smaller the distance between the display position of the left-eye image on the display and the display position of the right-eye image on the display becomes.
As a result, as the display size increases, the position of a stereoscopic image perceived by the viewer relative to the display gets closer to the viewer. Thus, as shown in FIG. 1A, the amount of image pop-out, i.e., the distance of a stereoscopic image from the display, is L1.
For the medium-size display, the amount of image pop-out, i.e., the distance of a stereoscopic image from the display, is L2, as shown in FIG. 1B.
For the small-size display, the amount of image pop-out, i.e., the distance of a stereoscopic image from the display, is L3, as shown in FIG. 1C.
In such a manner, as the display size increases, a stereoscopic image looks more popped out to the viewer.
Thus, as illustrated in FIG. 1D, a relationship of L1>L2>L3 is satisfied, where L1 indicates the amount of image pop-out for the large-size display, L2 indicates the amount of image pop-out for the medium-size display, and L3 indicates the amount of image pop-out for the small-size display.
Long hours of continuous viewing of a stereoscopic image that has a large amount of image pop-out to appear closer to viewers, as in the case in FIG. 1A, may cause some people to experience eyestrain, headache, and so on. When the amount of stereoscopic-image pop-out is small as in the case in FIG. 1C, there is a problem in that the viewer does not get an adequate sense of three dimensionality.
Since long hours of continuous viewing of a stereoscopic image that has a large amount of stereoscopic-image pop-out to appear closer to viewers, as in the case in FIG. 1A, may adversely affect young people such as children who are still growing, a safety guide has been set [e.g., refer to 3DC (http://www.3dc.gr.jp/jp/index.html)].
Thus, for three-dimensional image display, images having an optimum parallax corresponding to the display size are used for display.
For display of a three dimensional image on a display, configurations that utilize images having a different parallax corresponding to the display size have been available. For example, Japanese Unexamined Patent Application Publication No. 2008-172342 discloses a configuration for providing images having an appropriate parallax corresponding to a display device.
In the configuration disclosed in Japanese Unexamined Patent Application Publication No. 2008-172342, multiple images having different parallaxes from different viewpoints are photographed in advance, the parallaxes between the images are determined through use of information of a specific pattern included in the images, and images having a parallax that is suitable for the display device are selected and used. The information of the specific pattern is, for example, a human face in the images, and the parallaxes between the multiple images are determined based on the area of the human face.
The method disclosed in Japanese Unexamined Patent Application Publication No. 2008-172342, however, involves processing for extracting the information of the specific pattern through image analysis to determine the parallaxes. Consequently, cost for processing increases, and only an image including the specific pattern, for example, a facial image, can be appropriately processed. Thus, when the information of the specific pattern is not detected from an image, there is a problem in that the image is not appropriately processed. The method disclosed in Japanese Unexamined Patent Application Publication No. 2008-172342 also has a problem in that no consideration is given to the aforementioned safety guideline.